<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>块元素的特征</title>
    <style>
        div {
            height: 400px;
            background-color: red;
            margin-bottom: 20px;
        }
    </style>
</head>
<body>
    <!--
        块元素的特征：
        1.默认独占一行
        2.没有指定宽度时
        3.支持所有CSS命令
    -->
    <div></div>
    <div></div>
</body>
</html>